Department of Agriculture

HONOLULU — The stinging caterpillars that have been established on the Big Island since 2001, have been found at an Oahu nursery.  An infestation of nettle caterpillar (Darna pallivitta) has been confirmed and efforts are underway to attempt to contain the infestation in the nursery that is located in a relatively remote area in Central Oahu.

 

Workers at the nursery reported getting stung while moving plants from one site to another site on Friday, June 1. The nursery owner contacted the UH College of Tropical Agriculture & Human Resources (CTAHR) and extension agents then informed entomologists with the Hawaii Department of Agriculture (HDOA).  The nursery owner was instructed to immediately return all plants to the original site and immediately treat the second site with chemical insecticides.  The nursery also began treating the original site with insecticides over the weekend. 

 

On Monday, surveys were conducted by HDOA staff at both sites.  The original site was found to be infested with nettle caterpillar and bait stations were deployed.  The entire nursery is being chemically treated and surveys and monitoring will continue.  No nettle caterpillars were found at the second site, but bait stations were also set.

 

HDOA is asking Oahu residents and nurseries to look out for the nettle caterpillar and report suspected infestations to the State’s Pest Hotline, 643-PEST (7378).  Stings from the caterpillar may cause allergic reactions in those who are sensitive to the venom.  If stung, treatment recommendations include immediately washing the affected area with soap and water to remove any residue, applying ice to reduce swelling and consulting a physician to determine if further treatment is necessary.  Individuals who are sensitive to the venom should seek prompt medical attention, especially if they experience difficulty breathing or if they are stung in the eyes.

 

Nettle caterpillars grow to about one-inch long, white in color with black bands.  The caterpillar has distinct bristly spines that when touched, may cause a burning sensation that lasts about an hour.  (See attached Pest Advisory.) The adult moth is slightly smaller than a dime and is triangular in shape.  It is bicolored with the front 2/3 of the body a yellowish-brown and the posterior 1/3 is brownish.  The adult flies at night and hides under leaves during the day.  The caterpillar has been found primarily on the underside of the leaves of palm plants, grasses and lilies.

 

After the discovery of the nettle caterpillar in Hilo, HDOA began research on potential biological control agents – natural enemies of the nettle caterpillar that specifically attack this pest without harming native or other beneficial insects and the environment.  A predatory insect was found in Taiwan and has undergone testing in HDOA’s Insect Quarantine Facility in Honolulu.  HDOA is currently in the process of obtaining approval from federal and state regulatory entities to release the biocontrol insect.  This process is expected to take about another six months.

 

Until then, it is recommended that conventional chemical insecticides labeled for use on ornamental plants be applied to infested plants according to label directions.  Insecticides routinely recommended for use to control leaf-feeding caterpillars include carbaryl and acephate.  For those who prefer to use a non-toxic pesticide, Bt (Bacillus thuringiensis) sprays have proven to be effective against the larvae of various moths, including the nettle caterpillar.  Bt is not toxic to humans, other animals, and the environment.